1. Field of the Invention
The present invention relates to a manhole adjustment ring structured to facilitate the rapid adaptation of an existing manhole frame to accommodate resurfacing of a road in which it is disposed. The manhole adjustment ring of the present invention is substantially quick and easy to install despite potential variations in the precise dimensions of the existing manhole frame, is substantially durable, does not rattle, minimizes water infiltration, and is capable of withstanding repeated jarring from passing vehicles, while effectively accommodating a manhole cover in an elevated position.
2. Description of the Related Art
Manholes are a commonly used access to underground passageways beneath roads or other paved locations. Typically, the manholes are bordered by a manhole frame onto which a large sturdy manhole cover is disposed. As often heavy volumes of traffic pass over the manhole cover during normal use, the manhole cover is generally quite heavy and durable, formed of cast iron or another strong metal, and is positioned so as to completely cover and shield the manhole itself. Moreover, the manhole frame is sized so that the manhole cover is supportably maintained flush with the paved surface into which the manhole frame is disposed, thereby providing a generally uniform surface over which vehicles may pass.
As the original manhole frame is also usually formed of a strong, durable metal, such as cast iron, and is permanently connected to underground pipes and tunnels, the useful life of the manhole frame and manhole cover will often far exceed the life of the paved road into which it is positioned. Accordingly, it is often the case that a road having one or more manholes disposed therein must be repaved/resurfaced without having to repair the manhole cover or manhole frame. Of course, repaving a road calls for the addition of a new layer of pavement atop existing layers, such additional layers of payment rising above the rim of the existing manhole frames and thereby necessitating replacement or modification of the manhole frame.
Very often, however, the new layer of pavement is not as thick as the necessary height of a new seat portion of the manhole frame, and complete replacement of the entire existing manhole frame is not a practical option. Accordingly, a variety of adjustment fixtures have been developed in order to partially raise the seating region of the manhole frame a sufficient height to effectively seat the manhole cover. Such adjustment fixtures are typically rigid structures that are sized to precisely fit within the existing manhole frame. Unfortunately, however, variations often exist in the precise dimensions of different manhole frames such that the exact fitting of each adjustment frame must be achieved relative to the manhole frame into which it is to be disposed. Indeed, even small differences in the needed dimensions can result in either an impossible fit, or a small gap between the adjustment frame and the original frame. Furthermore, while it may appear that a small gap is not of major significance, due to heavy traffic and large amounts of stress which such manhole frames must withstand, even the smallest of gaps can lead to rattling and eventually to the loosening and/or damaging of the adjustment frame. As a result, a very precise fitting adjustment frame is preferred. Also, given that the adjustment fixture must expand to almost the precise dimensions of the existing manhole frame so as to effectively receive the manhole cover, existing devices often require an added layer of pavement, or generally protrude from the pavement creating a road hazard and providing an exposed surface that is more susceptible to wear or damage from heavy traffic.
Others in the art have attempted to develop adjustment frames which include an adjustable construction/configuration. Typically, these adjustable frames include a large number of thick segments secured to one another in an adjustable form. Such segmented devices, however, are very difficult and time consuming to install with precision because of the many adjustment variables associated with a highly segmented construction, and often do not fully and/or sufficiently engage the existing manhole frame, even after a large amount of adjustment and manipulation. Furthermore, such segmented designs often leave large gaps which can lead to water infiltration, and more rapid rusting and deterioration of the manhole frame and adjustment frame. Additionally, the often large exposed area of adjustment frame and the gaps in its construction also provide a large number of vulnerable areas in the adjustment frame's configuration, which are susceptible to yielding and deflection upon repeated impacts from the passage of motor vehicles thereover.
Accordingly, there is still a substantial need in the art for a manhole adjustment ring which is substantially quick and easy to install to a precise, mating dimension required by an existing manhole frame. Moreover, such an adjustment ring should minimize water infiltration and should be constructed so as to be substantially durable by minimizing gaps in its construction, and minimizing exposed areas, while still providing secure, accessible fit and retention of the manhole cover itself. Also, such an adjustment ring should attain the necessary dimension rapidly so as to eliminate protrusion thereof and of the manhole cover above the new layer of pavement.